For more than a decade, scientists have been waiting for Voyager 1 to leave the solar system. And for the last year or so we've been hearing conflicting reports. Last fall, Voyager was getting close. Then, in March, news outlets reported that it had crossed the threshold. But not so fast, NASA said, as it denied that the spacecraft had left the solar system.

The problem is that no one knows exactly what the spacecraft will encounter after it breaks through the magnetic bubble that surrounds our sun and that marks the area of the solar system. But one new study in The Astrophysical Journal Letters argues that, in fact, Voyager 1 may have already broken through the bubble without scientists realizing it and is now zooming through interstellar space.

Based on older models of the heliopause—the boundary between our sun's magnetic field and the interstellar magnetic field outside it—scientists expected to see three things when Voyager left the solar system: First, it should have stopped detecting charged particles emitted from the sun. Second, it should start detecting cosmic rays that originate from outside the solar system. Third, the instrument should detect a change in the direction of magnetic field. (While the sun's magnetic field orients roughly east to west, the interstellar magnetic field is expected to be north to south.)

In July and August 2012, Voyager 1 reached a strange region of space that fulfilled two of the three requirements: Solar particles stopped hitting the instrument's detectors, while cosmic rays started in for the first time. Nevertheless, since the magnetic field orientation stayed the same, NASA reported that the spacecraft hadn't yet broken through the heliopause.

But now, using a different model of what's happening out there, a group of scientists led by Mark Swisdak, an astrophysics researcher at the University of Maryland, are saying that Voyager 1 actually left the solar system last July. Their argument: Maybe interstellar space just isn't what we expected. According to the group's computer modeling, the two magnetic fields could actually be running in the same direction. Ars Technica explains: "[The new model] suggests that the interstellar field lines run directly up against the ones from our sun, at which point they execute a nearly right-angled turn, leaving the two sets to travel parallel."

The findings add to an ongoing astrophysics debate that heated up with the report in March of this year, when a paper published in Geophysical Research Letters claimed Voyager 1 left the solar system based on cosmic ray data and hydrogen and helium spectral data that looked as though they came from the interstellar medium. At the time, NASA scientists dismissed those arguments.

Now they seem to be a bit more open-minded:

"The fine-scale magnetic-connection model will become part of the discussion among scientists as they try to reconcile what may be happening on a fine scale with what happens on a larger scale," Voyager mission leader Ed Stone said in a NASA statement. "The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier."